Display Number of notes in each folder

[adrianchia]

In BoostNote Legacy each folder displays number of notes it has. This would be helpful especially when we have large number of notes for each folder.

[Rokt33r]

Should be able to implement it from here.
https://github.com/BoostIO/BoostNote.next/blob/master/src/cloud/lib/hooks/sidebar/useCloudSidebarTree.tsx